Newbie Cocoa Q: Help with pong

I'm trying to make a game of pong with Project Builder/Interface Builder and Objective-C. I'm using an NSView subclass for the playing field, an NSAffineTransform with an NSBezierPath for the ball and an NSView subclass for the two paddles. I have separated the ball and two paddles into three separate NSThreads. The ball and player paddle work ok, but I'm struggling with implementing the opponent AI. My player paddle movement method looks like this:

Make the enemy paddle move slow, to a certain extent. That way when the ball is traveling at an extreme angle, with a subsequently faster X velocity, and the cards are just right, the player will score. Making it react at a certain distance away from its paddle will also be another variable wich can make it behave differently. For a really whopper AI, make the enemy paddle aim for the corners.

A good example is Matt Diamond's "3D Paddlebash!", just look at the difficulty controls and you can really get a good grasp.

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This is the simplest AI I can think of, while still having it be effective. Enemyspeed is how many pixels the enemy paddle should move per frame. Enemyspeed is incorporated into the if statements so that the enemies paddle doesn't adjust itself back and forth when its right inline with the ball (you might see what I'm talking about later).

Thanks for the help, you posts made things much clearer. I will put all the methods into a single thread once I've debugged my collision detection method. I'll try for a more complex AI later, but I have to fix collision detection first. I got a basic AI method with: